The historically reversed novels of Harry Turtledove are those that one should read at least one adventure of sometime in his/her lifetime. With stories revolving around several reversed theories such as "What if the South had won the Civil War?" (Guns of the South) and some over "What if the Nazis had succeeded in taking over Europe?" (I don't know the title of that book off the top of my head) (;

It is really an ingenious variety of books for all adventurous history lovers.